Oct 13, 2010: Rain/Wind To Start Tomorrow

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Today was a mainly sunny day across the area, and temperatures were slightly cooler than those of yesterday. Starting tomorrow, however, clouds will return to the area, and a rapidly developing nor’easter will produce a round of heavy rain followed by windy conditions for the area, and will even produce several inches of snow for the higher elevations of the Northeast.

Thursday – Saturday: Storm, Wind Expected

Thursday: Tomorrow will start out partly cloudy, but cloud cover will increase in the morning due to an approaching storm, and the afternoon will bring cloudy skies with a SE wind expected. High temperatures will be in the mid to upper 50s inland, lower to mid 60s for the immediate NYC area, and lower 60s for Long Island/S CT.

The storm, meanwhile, will approach from the west, with a weak low pressure starting to develop in eastern Virginia, producing heavy rain in central/northern Virginia and Maryland. There is still some slight uncertainty with the development of the storm, and at this time, I am considering the latest GFS runs to be potential outliers, as they seem to be developing a low pressure well off the coast instead of the one in eastern Virginia, leading to a much more progressive and weaker storm that barely brings 1/4 inch of rain to the area. For this forecast, I am leaning towards the NAM/GGEM/ECMWF models, which the NAM and ECM have been more consistent.

Thursday Night: As the low pressure moves offshore and the trough becomes negatively tilted, the storm is expected to begin to rapidly intensify while moving northeast, producing a developing area of heavy rain to the west of the storm, which will make its closest approach to the area between 11 PM and 4 AM when the low pressure is just near the eastern end of Long Island with minimum pressure close to 990 mb.

The question is how far west the heavy rain extends, with some models focusing the heavy rain in Long Island and the others on northern New Jersey. More on this will come with tomorrow’s final forecast for the storm, when it will be possible to compare the latest data to the storm and make more accurate short term forecasts, but for now I am thinking the heaviest rain falls near NYC and western Long Island, with 1.5 to 2 inches of rain falling overnight.

Friday: The storm will peak in intensity during Friday afternoon, when a sub-980 mb low is expected over eastern Massachusetts. The storm will then have become vertically stacked, and will no longer be able to intensify, meaning that from Friday afternoon and on, the storm will begin to weaken along with the precipitation. A few showers are possible during the day on Friday, but with the storm to the northeast, Friday will mainly be a cloudy and chilly day, with highs in the lower to upper 50s. Windy conditions will also develop, with a WNW/NW wind gusting to 40-50 mph for the central/eastern parts of the area.

For the Northeast, however, while the storm is at its peak intensity, cold air will enter the storm from the northwest, leading to temperatures reaching the mid 30s in the higher elevations of the Northeast, including the Adirondacks and the Catskills. This will be enough to support snow falling over these areas, with as much as several inches of wet snow possible. Widespread heavy rain will affect central/northern New England, which will begin to weaken by the evening hours.

Storm Summary:

By the time that the storm is over, at least 1 to 2.5 inches of rain are expected for the area, with the highest amounts towards east central NY further east into central New England. It is possible that the GFS ends up being correct in its eastern solution, and while at this time I am leaning towards the western solutions, it is possible that tomorrow’s update could be different, especially as details become clearer. More details will be posted with tomorrow’s update, as well as rain and snow maps.

Longer Range: Chilly, Then Cold?Tomorrow’s update will also cover more on the longer range, including a potential cold spell that may affect the area starting on October 20. Stay tuned for more details on this time frame.

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